When David Cameron declared that his government would "end the incarceration of children for immigration purposes once and for all", those familiar with the horror of it were cautiously optimistic. That cautious optimism is now tempered with anxiety that his passion for radical reform of this grotesque abuse of human rights is on the wane. The emerging picture is at best confusing, at worst ominous.

Last week the charity Medical Justice, whose doctors, lawyers and supporters assist detainees in immigration detention pro bono, published a report. The title – State Sponsored Cruelty: Children in Immigration Detention – was taken from Nick Clegg's attack on Gordon Brown in an open letter last year: "Very young children who find themselves locked up even though they've done nothing wrong are suffering weight loss, post-traumatic stress disorder and long-lasting mental distress," Clegg wrote. "How on earth can your government justify what is in effect state-sponsored cruelty?" The report catalogues the effects of immigration detention on children. Three have attempted suicide, some have regressed, others become withdrawn. Many have shown signs of deep disturbance.

So far, little has been done to implement Cameron's pledge and follow up on Clegg's passionate denunciation. A review was set up in June to look into the ending of the detention of children, led by David Wood, strategic director for criminality and detention at the UK Border Agency. Perhaps Wood has changed his mind, but a year ago he told the Commons home affairs select committee: "Our immigration policy would be in difficulty if we did not have that ability to detain [families] because it would act as a significant magnet to families from abroad … once they got here they could just say, 'I am not going'."

Pilot programmes were set up in June to run during the review period, charged with finding alternatives to detention. Their findings have yet to be made public but a document leaked in August suggested that the priority was boosting removal rates, rather than humanitarian considerations.

Campaigners are worried. Bail for Immigration Detainees (BID) has provided legal advice to hundreds of families since 2001. Like other groups involved with refugees and asylum seekers, BID was invited to provide information to the review. Sarah Campbell, BID's research and policy manager, says: "The information available to us suggests that, at best, these pilots have been given inadequate attention by officials. At worst, they have been set up to fail by an agency which appears to have little desire to implement the government's commitment to ending child detention." A Home Office spokesman told me there is no information publicly available on the pilot schemes. He added that there would "always have to be some sort of detention". Asked what sort, he replied that it would depend on one's definition of detention.

The Home Office, it seems, is having trouble defining detention, as borne out by conflicting information given to me last week by its press office. On Tuesday, a spokesman said there had been 24 families in immigration detention since May. On Wednesday it sent an email which said that figure was wrong because it failed to include those held under immigration legislation in mother and baby units in prisons and those refused entry at borders and held in immigration removal centres pending deportation – some of whom are not asylum seekers. It's a complex picture. But whichever way you cut it, these are children detained under immigration law, despite Cameron's promise to end the incarceration of children for immigration purposes.

The Home Office email said that between May and August, 45 families – including 80 children – had been detained. The next day the figure changed again – 59 children from 32 families have been in immigration detention since May, 31 of the children at Yarl's Wood immigration removal centre. I was told these are not official statistics but "purely UK Border Agency management information". I was asked to refer to them as "figures supplied by the Home Office or something along those lines".

Confused? My original question was how many children had been held in immigration removal centres since May. I didn't ask about families in prisons or people who had been refused entry at borders. Could the Home Office response suggest that prisons and holding centres at borders, as well as the detention removal centres, are being used to detain families with children? Ghosting families around the prison estate would render them less visible.

The last point on Wednesday's email announced: there are no children presently in detention. So where have the 80 or 59 children gone? Forcibly removed? Destitute? Given leave to remain? And then Thursday's email revealed there were two children in Yarl's Wood. In July, Clegg said the family unit there was to be closed.

"The asylum system is a source of moral shame," Clegg said back in March. It was, he added, "a moral outrage" that 1,000 children had been imprisoned last year. In May immigration minister Damian Green joined in, saying he found it disturbing to see children locked up at Yarl's Wood: "That is one of the things that impels our policy." But by August Green's tone had shifted. "I am bending over backwards to avoid the detention of children, but we are still not sure that if we said we would never detain a child even for a minute then we would effectively be able to remove families that had no right to be in this country."

Amid this confusion and obfuscation one thing is clear, and that is that the powerful, substantial and growing lobby of professionals and campaigners will go on watching what happens to these families and do all in their power to prevent a continuation of the state-sponsored cruelty that so outraged Nick Clegg.